Question 1

How do I make a casting mold of my own model?

Accepted Answer

Upload an STL, 3MF or OBJ (or try the example, a chess pawn). The tool shows the model's size and volume, checks for undercuts and offers five kinds of mold with a recommendation. Pick one, set the parameters and material — before downloading you see the material and plastic use and whether the parts fit your printer bed.

Question 2

Which mold should I choose: plastic, silicone or plaster?

Accepted Answer

A 2-part plastic mold is the fastest: you pour resin, plaster or wax straight into the printed halves, but only if the model has no undercuts. If the model won't come out of two halves, a 3–4-part plastic mold does the job: each part comes off in its own direction. An open-top silicone mold suits models with a flat base, which becomes the pour opening. A 2-part silicone mold suits rounded models: flexible silicone releases even from undercuts. Plaster is rigid and cheap — used for wax, concrete and slip. The cards show the recommendation for your model.

Question 3

How do I make a 2-part silicone or plaster mold?

Accepted Answer

The tool gives you three kinds of printed parts: a mold box; a bed — a plate with a cavity matching the lower half of the model up to the parting line, with corner keys and grooves; and sprue and vent formers. Place the model in the bed, pour the first half, flip, remove the bed, apply release and pour the second half. Step-by-step instructions with the silicone or plaster amount for each half are on the page and in a file.

Question 4

How much silicone or plaster does a mold need?

Accepted Answer

The box cavity minus the model and formers — for each half separately. Silicone weighs about 1.1 g/ml, so 100 ml is roughly 110 g; for plaster the tool splits the mix into dry plaster and water. Add 5–10% for what stays in the cup — you can choose the allowance.

Question 5

What are undercuts and why can't I download some molds?

Accepted Answer

An undercut is a part of the model the mold catches on — like a pawn's head being wider than its neck. The tool picks the parting plane with the fewest undercuts and highlights them in red. Such a cast can't come out of a rigid two-part mold, plastic or plaster, so download is closed. The tool then suggests a 3–4-part plastic mold (if each part can come off in its own direction) or silicone: flexible silicone releases even from undercuts.

Question 6

Can I pour epoxy or chocolate straight into a printed mold?

Accepted Answer

Without release agent, epoxy bonds firmly to PLA and PETG, and printed plastic is not food-safe. That is why for chocolate and ice the tool defaults to a master for a silicone mold: you print a box with positives, cast a food-grade silicone mold from it and pour chocolate or water into that. It is the safer route for epoxy too.

Question 7

Why is this tool a demo?

Accepted Answer

We cannot check every mold by hand, and a large mold takes hours to print and hundreds of grams of plastic. Before printing, open the file in your slicer and check the size, wall thickness, undercuts and plastic use. Every file is tagged _DEMO.

Question 8

Which plastic should I print the mold in?

Accepted Answer

PLA is fine for silicone, plaster and concrete. For hot wax and soap base use PETG or ASA: PLA softens from 55–60 °C. Thinner layers and clean walls give a smoother cast, because every layer line shows on it.

Question 9

What about molds with three or more parts?

Accepted Answer

There's a 3–4-part plastic mold for resin, wax, plaster and concrete when the model won't come out of two halves. The tool picks two perpendicular parting planes and a layout — a lid and two halves, a base and two halves, or four parts — checks every part for undercuts and adds keys, a sprue, vents, strap grooves and part numbers in take-apart order. You can move the planes by hand. If the cast won't come out even of 3–4 parts, the tool says so honestly and suggests a silicone mold.

Mold Maker: a casting mold from your model

Upload a model (STL, 3MF, OBJ) and we'll make a casting mold of it

Frequently asked questions